Security related integrated circuits (ICs) including secret information such as, for example, a secret key used for encryption or validation purposes, are typically equipped with anti-tamper structures for preventing unauthorized access of this secret information contained in the IC.
In U.S. Pat. No. 7,005,733 one such anti-tamper structure is disclosed according to which a light-source is positioned on the surface of an IC having a plurality of light sensors. The IC-light source assembly is encapsulated by a light-transmissive material having a plurality of randomly dispersed particles, and the encapsulation is surrounded by a outer covering which is light reflective on the inside and does not allow entry of light from the outside. When the IC-light source assembly is packaged in this manner, light emitted by the light source interacts with the dispersed particles and is reflected by the inside of the outer covering to form a characteristic interference pattern which is sensed by the light sensors. This characteristic pattern is used to produce a cryptographic key. When the package is tampered with so that the outer covering is perforated, some of the light will escape from the package and the interference pattern sensed by the detectors will be altered, and the key will thereby be changed.
A drawback of the anti-tamper structure disclosed in U.S. Pat. No. 7,005,733 is that it severely restricts the application range for the IC by requiring the IC to be surrounded by a transparent encapsulant which is enclosed by a reflective outer covering.
In particular, in order to protect the backside of the IC from being tampered with, the transparent encapsulant and reflective outer covering must surround the entire IC, which further restricts the application range by necessitating a package having connector pins surrounding the perimeter of the package.
Accordingly, there is a need for an improved tamper-protected semiconductor device which is suitable for a wider range of applications.
In particular, there is a need for providing a tamper-protected semiconductor device, that allows more flexibility in packaging and is therefore more cost-effective.